Methods of providing semiconductor layers from amic acid salts

ABSTRACT

A semiconductor layer and device can be provided using a method including thermally converting an aromatic, non-polymeric amic acid salt to a corresponding arylene diimide. The semiconducting thin films can be used in various articles including thin-film transistor devices that can be incorporated into a variety of electronic devices. In this manner, the arylene diimide need not be coated but is generated in situ from a solvent-soluble, easily coated aromatic, non-polymeric amic acid salt at relatively lower temperature because the cation portion of the salt acts as an internal catalyst.

FIELD OF THE INVENTION

This invention relates to methods of providing semiconductor layers andarticles containing same from a unique class of organic non-polymericamic acid salts. These methods include thermally converting the amicacid salts into corresponding arylene diimides at lower temperatures.This invention also relates to methods of making the organicnon-polymeric amic acid salts.

BACKGROUND OF THE INVENTION

Considerable efforts have been made to discover new organicsemiconductor materials that can be used in FET's to provide switchingor logic elements in electronic components, many of which requiresignificant mobilities well above 0.01 cm²/V.sec, and current on/offratios (hereinafter referred to as “on/off ratios”) greater than 1000.Organic FET's (“OFET's”) having such properties can be used forelectronic applications such as pixel drivers for displays andidentification tags. However, most of the compounds exhibiting thesedesirable properties are “p-type” or “p-channel,” meaning that negativegate voltages, relative to the source voltage, are applied to inducepositive charges (holes) in the channel region of the device.

As an alternative to p-type organic semiconductor materials, n-typeorganic semiconductor materials can be used in FET's where theterminology “n-type” or “n-channel” indicates that positive gatevoltages, relative to the source voltage, are applied to induce negativecharges in the channel region of the device.

Moreover, one important type of FET circuit, known as a complementarycircuit, requires an n-type semiconductor material in addition to ap-type semiconductor material. Simple components such as inverters havebeen realized using complementary circuit architecture. Advantages ofcomplementary circuits, relative to ordinary FET circuits, include lowerpower dissipation, longer lifetime, and better tolerance of noise. Insuch complementary circuits, it is often desirable to have the mobilityand the on/off ratio of an n-channel device similar in magnitude to themobility and the on/off ratio of a p-channel device. Hybridcomplementary circuits using an organic p-type semiconductor and aninorganic n-type semiconductor are known, but for ease of fabrication,an organic n-channel semiconductor material would be desired in suchcircuits.

Only a limited number of organic materials have been developed for useas a semiconductor n-channel in OFET's. One such material,buckminsterfullerene C₆₀, exhibits a mobility of 0.08 cm²/V.sec but itis considered unstable in air (Haddon et al. Appl. Phys. Let. 1995, 67,121). Perfluorinated copper phthalocyanine has a mobility of 0.03cm²/V.sec and is generally stable to air operation, but substrates mustbe heated to temperatures above 100° C. in order to maximize themobility in this material (Bao et al. Am. Chem., Soc. 1998, 120, 207).Other n-channel semiconductors, including some based on a naphthaleneframework, have also been reported, but with lower mobilities. One suchnaphthalene-based n-channel semiconductor material,tetracyanonaphthoquino-dimethane (TCNNQD), is capable of operation inair, but the material has displayed a low on/off ratio and is alsodifficult to prepare and purify.

Aromatic tetracarboxylic diimides, based on a naphthalene aromaticframework, have also been demonstrated to provide n-type semiconductors.Thus, in naphthalene diimide-based OFET's in U.S. Pat. No. 6,387,727(Katz et al.) demonstrated n-channel mobilities up to 0.16 cm².V.sec.Comparable results were obtained with bottom contact devices, but athiol underlayer had to be applied between the gold electrodes and thesemiconductor as described. In the absence of the thiol underlayer, themobility of naphthalene diimide derivatives in U.S. Pat. No. 6,387,727was found to be orders of magnitude lower in bottom-contact devices.This patent also discloses fused-ring tetracarboxylic diimide compounds,one example of which is N,N′-bis(4-trifluoromethyl benzyl)naphthalenediimide. The highest mobilities of 0.1 to 0.2 cm²/V.sec were reportedfor N,N′-dioctyl naphthalene diimide.

In a different study, using pulse-radiolysis time-resolved microwaveconductivity measurements, relatively high mobilities have been measuredin films of naphthalene diimides having linear alkyl side chains(Struijk et al., J. Am. Chem. Soc. Vol. 2000, 122, 11057).

U.S. Patent Application Publication 2002/0164835 (Dimitrakopoulos etal.) discloses n-channel semiconductor films made from perylene diimidecompounds, as compared to naphthalene-based compounds, one example ofwhich is N,N′-di(n-1H,1H-perfluorooctyl) perylene diimide. Substituentsattached to the imide nitrogens in the diimide structure comprise alkylchains, electron deficient alkyl groups, and electron deficient benzylgroups, and the chains preferably having a length of four to eighteenatoms. Devices based on materials having a perylene framework used asthe organic semiconductor have low mobilities, for example 10⁻⁵cm²/V.sec for perylene tetracarboxylic dianhydride (PTCDA) and 1.5×10⁻⁵cm²/V.sec for N,N′-diphenyl perylene diimide (PTCDI-Ph) (Horowitz et al.Adv. Mater. 1996, 8, 242 and Ostrick et al. J. Appl. Phys. 1997, 81,6804).

In perylene and naphthalene diimide based OFET's, many experimentalstudies have demonstrated that morphology of the thin film has strongimpact on the device performances. Theoretical calculation andexperimental characterization (particularly X-ray diffraction), haveshown that the molecular packing in PDI is very sensitive to the sidechains (Kazmaier et al. J. Am. Chem. Soc. 1994, 116, 9684). In perylenediimide based n-channel OFET devices, changing the side chain fromn-pentyl to n-octyl increases the field effect mobility of from 0.055cm²/V.sec to 1.3 cm²/V.sec, respectively (Chesterfield et al. J. Phys.Chem. B 2004, 108, 19281). Such sensitivity to the type of side-chain isa manifestation of an aggregation effect and it provides potentially aneffective way to control and optimize the molecular packing for enhancedπ-orbital overlap between neighboring molecules, a necessary forefficient carrier transport. U.S. Pat. No. 7,422,777 (Shukla et al.)discloses N,N′-dicycloalkyl-substituted naphthalene diimide compounds,which in thin films, exhibit optimum packing and exhibit n-channelmobility up to 6 cm²/V.sec in OFET's. U.S. Pat. No. 7,579,619 (Shukla etal.) discloses N,N′-di(arylalkyl) substituted naphthalene diimidecompounds that exhibit high n-channel mobility up to 3 cm²/V.sec intop-contact OFET's.

A variety of naphthalene diimides have been made and tested for n-typesemiconducting properties. In general, these materials, as an n-typesemiconductor, have provided n-channel mobilities up to 6 cm²/V.secusing top-contact configured devices. However, besides charge mobility,improved stability and integrity of the semiconductor layer areimportant goals.

U.S. Patent Application Publication 2005/0176970 (Marks et al.)discloses improved n-channel semiconductor films made of mono- anddiimide perylene and naphthalene compounds wherein the nitrogen and coreare substituted with electron withdrawing groups. Substituents attachedto the imide nitrogen atoms in the diimide structure can be selectedfrom alkyl, cycloalkyl, substituted cycloalkyl, aryl, and substitutedaryl groups. However, this publication fails to suggest any comparativeadvantage of using cycloalkyl groups on the imide nitrogen atoms.Accordingly, mobilities obtained from perylene diimides containing ofN-octyl and N-cyclohexyl are virtually indistinguishable (see Example 10of the publication). Furthermore, the highest mobilities reported inthis reference are 0.2 cm²/V.sec and the reference fails to showexperimental data with respect to naphthalene compounds and require thattheir core be cyano di-substituted.

Aromatic tetracarboxylic diimides, based on a naphthalene and perylenearomatic framework have been widely used as n-type semiconductormaterials (Newman et al. Chem. Mater. 2004, 16, 4436-4451). Relativelylow mobilities have been measured in films of naphthalenetetracarboxylic diimides having linear alkyl side chains usingpulse-radiolysis time-resolved microwave conductivity measurements. SeeStruijk et al. “Liquid Crystalline Perylene Diimides: Architecture andCharge Carrier Mobilities” J. Am. Chem. Soc. Vol. 2000, 122, 11057.However, TFT's based on N,N′-dicyclo-substituted naphthalene diimideexhibit mobility up to 5 cm²/V.sec (Shukla et al. Chem. Mater. 2008, 20,7486-7491). U.S. Pat. No. 6,387,727 (Katz et al.) discloses fused-ringtetracarboxylic diimide compounds, such as N,N′-bis(4-trifluoromethylbenzyl)naphthalene-1,4,5,8,-tetracarboxylic acid diimide. The highestmobilities reported in this patent is between 0.1 and 0.2 cm²/V.sec forN,N′-dioctyl naphthalene-1,4,5,8-tetracarboxylic acid diimide.

It is widely recognized that the morphology and microstructure of anorganic thin film has a strong impact on the charge carrier mobility andOTFT device characteristics. In general, organic materials that formhighly oriented polycrystalline thin films exhibit high charge carriermobility. At the molecular level, it is the basic chemical structure ofthe molecule that controls intermolecular interactions that determinesif a material will be crystalline or amorphous. The extent of π-stackingbetween the molecules determines whether the organic film will be highlycrystalline or totally amorphous. Thus, to have well-defined thin filmmorphology, it is necessary to control materials on the molecular scale.This necessitates adapting the basic structure of semiconductingmolecules in a way that results in an optimum crystalline packingarrangement.

It is known that diimide based semiconductors are very sensitive to thesubstitutions on the nitrogen atoms of the diimide rings. Suchsensitivity to the side-chain is a manifestation of subtle changes indiimide aggregation in solid state and provides potentially an effectiveway to control and optimize the molecular packing for enhanced π-orbitaloverlap between neighboring molecules, a necessity for efficient carriertransport. Accordingly, U.S. Pat. No. 7,422,777 (Shukla et al.)discloses N,N′-dicycloalkyl-substituted naphthalene diimide compounds,which in thin films, exhibit optimum packing and exhibit n-channelmobility up to 6 cm²/V.sec in OFET's. In another example, U.S. Pat. No.7,579,619 (Shukla et al.) discloses N,N′-di(arylalkyl) substitutednaphthalene diimide compounds that exhibit high n-channel mobility up to3 cm²/V.sec in top-contact OFET's. These materials consistently exhibithigher mobility compared to a naphthalene tetracarboxylic diimide havingphenyl substituents.

U.S. Patent Application Publications 2008/0135833 (Shukla et al.) and2009/0256137 (Shukla et al.) describe n-type semiconductor materials forthin film transistors that include configurationally controlledN,N′-dicycloalkyl-substituted naphthalene 1,4,5,8-bis-carboximidecompounds or N,N′-1,4,5,8-naphthalenetetracarboxylic acid imides havinga fluorinated substituent, respectively. In these cycloalkyl-substitutednaphthalene diimide derivatives, the effect of the alkyl groupconfiguration in the cycloalkyl ring affects the aggregation, and hencethe carrier mobility, in solid state.

Recently, dicyanated arylene diimide semiconductors based on peryleneand naphthalene diimide cores have been developed that are solutionprocessable and show environmental stability (Adv. Funct. Mater. 2008,18, 1329-1339). The latter characteristics arise from cyano groupaddition to the core, which increases solubility by decreasing molecularplanarity and stabilizes charge carriers by lowering the energies of thelowest unoccupied molecular orbital's associated with electrontransport. While high temperature vapor deposited devices using thesematerials show good mobilities (ca. 0.1-0.5 cm²/V.sec; Jones et al. Adv.Funct. Mater. 2008, 18, 1329-1339), solution coated device usually givelower mobility and exhibit low I_(on)/I_(off) ratio.

As is clear from the foregoing discussion, the development of newsemiconducting materials, both p-type and n-type, continues to be anenormous topic of interest and unpredictable as to the semiconductiveproperties of various compounds. Among n-type diimide based materials,the highest charge carrier mobility (ca. 5.0 cm²/V.sec) in thin filmtransistors has been observed with N,N′-dicyclohexyl-naphthalenediimide. However, the poor solubility of this material limits itspractical application potential. Although, as discussed above,dicyanated arylene diimide semiconductors based on perylene andnaphthalene diimide cores are solution processable and showenvironmental stability their carrier mobility is low. To attainsolubility extensive molecular modification have to be made whichusually lowers the crystallinity of the material (for example see et al.Adv. Funct. Mater. 2008, 18, 1329-1339) that usually results in lowermobility in OTFT devices.

Efforts continue to improve performance of n-type organic semiconductormaterials in OTFT's and technology for their manufacture and use.Specifically there continues to be research efforts to find newmaterials and processes that are useful in n-type semiconductingmaterials which compounds do not require significant structuralmodification to achieve processability and optimum crystalline packing.

Amic acids are usually more soluble than aromatic anhydrides they arederived from. One attractive way of obtaining solution-processed thinfilms of diimide-based semiconductors is to solution coat an amic acidand, then by thermal dehydration reaction, convert it to thecorresponding diimide.

The dehydration of amic acids, derived from the reaction of cyclicanhydrides with primary amines, to yield imides is a general method forthe preparation of this important class of heterocyclic compounds and isof major commercial significance in the conversion of polyamic acids topolyimides (Kreuz, Endrey, Gay, and Sroog, J. Polym. Sci., Part A, 4,2607 (1966), and references contained therein.). As polyimides derivedfrom phthalamic acids possess many desirable attributes, this class havematerials have found applications in many technologies ranging fromdielectrics in microelectronics to high temperature adhesives tomembranes (for example see Mittal, Polyimides and Other High TemperaturePolymers: Synthesis, Characterization and Applications vol. 1 to 5).Most of the detailed studies have concentrated on preparation ofpolyphthalamic acids and their conversion to polyimides in solid films(for example, see Kim et al. in Polymer 40, 1999, pp 2263-2270, andreferences cited therein). In contrast, little is known about thedehydration reactions of amic acids derived from anthracene,naphthalene, and perylene anhydrides or anthracene, naphthalene, andperylene tetracarboxylic acid dianhydrides. Fabienne et al have recentlyreported mechanistic studies of polycondensation reactions ofnaphthalene anhydride leading to naphthalimide polymers (Piroux,Mercier, and Picq, High Performance Polymers (2009), 21(5), 624-632).

Genies et al. have reported synthesis of soluble sulfonated naphthalenicpolyimides, derived from naphthalene dianhydride, as materials forproton exchange membranes (Genies et al. Polymer 42 (2001) 359-373).

Copending and commonly assigned U.S. Ser. No. 12/770,803 (filed Apr. 30,2010 by Shukla, Meyer, and Ahearn) describes novel aromatic amic acidsand amic esters that can be thermally converted to corresponding arylenediimides that are formed into semiconductive layers for various articlesand devices. These compounds are advantageous in that the semiconductivelayers can be formed in situ while the precursor compounds are readilycoated from organic solvents.

Salts of poly(amic acids) have also been shown to undergo thermalimidization reaction to generate polyimides. Facinelli et al. haveprepared thermoplastic polyimides via poly(amic acid) salt precursors(see Facinelli et al. Macromolecules 1996, 29, 7342-7350). Thesepoly(amic acid) salts were prepared in heterogeneous reactions of thepoly(amic acid)s using quaternary ammonium bases or triethylaminedissolved in methanol or water to yield soluble salts which were thenmelt imidized in air at 250 or 300° C. for 30 minutes. Ding et al. haveprepared polyimide based membranes from poly(amic acid) salts (see Dinget al. Macromolecules 2002, 35, 905-911). This publication shows thatpoly(amic acid) tertiary amine salts can be quantitatively imidized at alower temperature than the poly(amic acid) or poly(amic acid) quaternaryamine salts of identical backbone structure. Xu et al. have synthesizedpolyimides from a diamine-acid salt and a dianhydride in the presence ofexcess triethylamine, thereby avoiding the use of air-sensitive aromaticdiamine compounds as monomers (Xu et al., Macromol. Rapid Commun. 2000,21, 481-484). Yang et al. have also prepared and characterized poly(amicacid) salts of pyromellitic dianhydride (Yang et al. MacromolecularResearch, 2004, Vol. 12, No. 3, pp 263-268). Polyimide multilayer thinfilms prepared from poly(amic acid) and poly(amic acid) ammonium saltare described in Macromolecular Research, 2008, Vol. 16, No. 8, pp725-733. WO 95/04305 (Flattery et al.) discloses a photosensitivecomposition of a fluorinated poly(amic acid) aminoacrylate salt.

WO 92/00283 (Goze et al.) discloses the use of N,N′-disubstituted amicacid ammonium salts, their use as surfactants, emulsifiers, suspendingagents, and conditioning agents in shampoos. This publication does notteach thermal imidization reaction of such salts. It also fails todisclose amic acids salts of naphthalene or perylene tetracarboxylicacids.

Kim et al., J. Phys. Org. Chem. 2008, 21 731-737 describes the formationof amic acid salts in the hydrolysis of certain aliphatic naphthalenediimides. However, the publication does not isolate these salts or teachtheir thermal imidization reaction. EP 0 805 154A1 (Iwasawa et al.)discloses certain N,N-disubstituted amic acid derivatives as in-vivoinhibitors of protein-farnesyl transferase (PFT).

The use of such amic acid and amic ester precursor compounds have anumber of advantages, as described in the U.S. Ser. No. 12/770,803described above, but there is a need to provide semiconductive layers atlower temperatures, or even at room temperature, to improvemanufacturing processes.

SUMMARY OF THE INVENTION

This invention provides a method for preparing a thin film transistordevice comprising the steps of:

A) depositing a gate insulator layer on a electrically conductingsubstrate, and

B) depositing a layer of an aromatic, non-polymeric amic acid salt onthe gate insulator layer.

This method can further comprise:

C) thermally converting the aromatic, non-polymeric amic acid salt toform an arylene diimide compound to form an organic semiconductor layer,and

D) depositing one or more of sets of electrically conductive sourceelectrodes and drain electrodes on the organic semiconductor layer.

Still further, in some embodiments, each electrically conductive sourceand drain electrode are spaced apart so that they are separated by, andelectrically connected with, the organic semiconductor layer, and themethod also includes:

forming a gate electrode spaced apart from the organic semiconductorlayer.

This invention also includes a method for preparing a thin film of anarylene diimide precursor comprising the steps of:

A) adding a dianhydride to an organic solvent and stirring the resultingmixture to obtain a solution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an aromatic, non-polymeric amic acid salt,

C) applying the dianhydride solution to a substrate to form a coating,and

D) removing the organic solvent from the coating to form a layer of thearomatic, non-polymeric amic acid salt.

Still in other embodiments, the method comprising, not necessarily inorder, the following steps:

providing the electrically conducting substrate,

providing a gate electrode material over the substrate,

providing a gate dielectric over the gate electrode material, and

depositing the aromatic, non-polymeric amic acid salt over the gatedielectric.

Yet other embodiments of this invention include a method comprising, notnecessarily in order, the following steps:

A) providing an electrically conductive substrate,

B) providing a gate electrode material over the substrate,

C) providing a gate dielectric over the gate electrode material,

D) depositing a organic solvent solution or dispersion of an aromatic,non-polymeric amic acid salt over the gate dielectric, and

E) evaporating the organic solvent to produce a thin film of thearomatic, non-polymeric amic acid salt.

Thus, the method can comprise, not necessarily in order, the followingsteps:

providing the electrically conducting substrate,

providing a gate electrode material over the substrate,

providing a gate dielectric over the gate electrode material,

depositing the aromatic, non-polymeric amic acid salt over the gatedielectric,

converting the aromatic, non-polymeric amic acid salt to an arylenediimide compound, and

providing an electrically conductive source electrode and a drainelectrode contiguous to the organic semiconductor layer.

In other embodiments, a method for preparing a thin film of an arylenediimide compound comprises the steps of:

A) adding a dianhydride to an organic solvent and stirring the resultingmixture to obtain a solution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an aromatic, non-polymeric amic acid salt,

C) adding an amine catalyst to the solution obtained in Step B in anamount of from about 0.5 to about 2 weight %,

D) applying the solution of Step C to a substrate to form a coating,

E) removing the organic solvent from the coating to form a layer of thearomatic, non-polymeric amic acid salt, and

F) thermally converting the aromatic, non-polymeric amic acid salt to anarylene diimide compound to form an organic semiconductor layer.

In addition, a method for fabricating a thin-film semiconductor device,consists essentially of, not necessarily in the following order, thesteps of:

A) applying onto a substrate an organic solvent solution of an aromatic,non-polymeric amic acid salt and an amine catalyst to form a coating,

B) evaporating the solvent to produce a thin film of the aromatic,non-polymeric amic acid salt, and

C) heating the thin film of the aromatic, non-polymeric amic acid saltfor a period of time sufficient to convert the aromatic, non-polymericamic acid salt to form an organic semiconductor thin film consistingessentially of a corresponding arylene diimide compound,

D) forming a spaced apart electrically conductive source electrode anddrain electrode, wherein the electrically conductive source electrodeand the drain electrode are separated by, and electrically connectedwith, the organic semiconductor thin film, and

E) forming a gate electrode spaced apart from the organic semiconductorthin film.

In addition, a method comprises, not necessarily in order, the followingsteps:

A) providing a substrate,

B) providing a gate electrode material over the substrate,

C) providing a gate dielectric over the gate electrode material,

D) depositing a organic solvent solution or dispersion of an aromatic,non-polymeric amic acid salt over the gate dielectric,

E) evaporating the organic solvent to produce a thin film of thearomatic, non-polymeric amic acid salt,

F) heating the thin film of the aromatic, non-polymeric amic acid saltat a temperature and for a period of time sufficient to convert thearomatic, non-polymeric amic acid salt to the corresponding arylenediimide compound to provide an organic semiconductor thin film, and

G) providing an electrically conductive source electrode and a drainelectrode contiguous to the organic semiconductor thin film.

The aromatic, non-polymeric amic acid salts described herein can be usedto prepare thin films that are thermally convertible to correspondingsemiconductive arylene diimide compounds, such as, naphthalene diimides.Thus, the arylene diimides are obtained via solid state thermaldehydration imidization reaction of the organic-soluble aromatic,non-polymeric amic acid salts. The aromatic, non-polymeric amic acidsalts can be easily prepared in environmentally friendly solvents likemethanol, ethanol, water, or mixtures thereof.

The advantages of this invention are achieved by preparing thin films ofsemiconducting arylene diimides by solid state thermal dehydrationimidization reaction of an aromatic, non-polymeric amic acid salt or amixture of salts. The presence of the cation in the salt enables lowertemperature conversion to the arylene diimides. In other words, thecation appears to act as a catalyst in the thermal conversion reaction.The low temperature processing combined with readily available materialsand ease of deposition of thin films over large areas due to solubilityof the aromatic, non-polymeric amic acid salts provide an inexpensiveand more convenient approach to the fabrication of thin film transistordevices and other semiconductive articles. Furthermore, since, comparedto corresponding diimides, aromatic, non-polymeric amic acid salts arereadily soluble in a variety of solvents and water, the presentinvention enables their coating on a variety of substrates withoutadditional preparations (such as applying an extra adhesion promotionlayer onto the substrate or modifying the substrate surface in someother manner).

The present invention and its advantages will become more apparent whentaken in conjunction with the following description, drawings, and theillustrative working examples provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a through 1 d illustrate cross-sectional views of four possibleconfigurations for an organic field effect transistor. FIGS. 1 a and 1 bhave a bottom gate configuration and FIGS. 1 c and 1 d have a top gateconfiguration

FIGS. 2 a, 2 b, and 3 are graphical plots of synthetic data obtained inInvention Example 2 below.

FIGS. 4 a and 4 b are graphical plots of performance data obtained forthe devices described below in Invention Example 2.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, “a” or “an” or “the” are used interchangeably with “atleast one,” to mean “one or more” of the components or elements beingdefined. For example, mixtures of aromatic, non-polymeric amic acidsalts can be used to provide mixtures of arylene diimide compounds inthe semiconductive layers or coatings. In addition, “solvent” caninclude mixtures of solvents in which the aromatic, non-polymeric amicacid salts are dissolved or dispersed.

The aromatic, non-polymeric amic acid salts used in this invention are“bis” compounds. By “non-polymeric” in reference to the aromatic,non-polymeric amic acid salts, we mean that the compounds do not containtwo or more recurring “bis” units in a chain.

Unless otherwise specifically stated, use of the term “substituted” or“substituent” means any group or atom other than hydrogen. Additionally,when the term “group” is used, it means that when a substituent groupcontains a substitutable hydrogen, it is also intended to encompass notonly the substituents unsubstituted form, but also its form to theextent it can be further substituted (up to the maximum possible number)with any other mentioned substituent group or groups (mentioned for thesame position) so long as the substituent does not destroy propertiesnecessary for semiconductor utility. If desired, the substituents canthemselves be further substituted one or more times with acceptablesubstituent groups. When a molecule can have two or more substituents,the substituents can be joined together to form an aliphatic orunsaturated ring unless otherwise provided.

Aromatic, Non-Polymeric Amic Acid Salts and Compositions

n-Channel organic semiconductor layers (or thin films) can include oneor more of arylene diimide compounds. This layer is capable ofexhibiting a field effect electron mobility that is greater than 0.0001cm²/V.sec, or greater than 0.1 cm²/V.sec, or more likely greater than 1cm²/V.sec. In many useful embodiments, the thin organic semiconductorfilms (and the devices containing the films) exhibit a field effectelectron mobility that is greater than 0.01 cm²/V.sec.

In addition, the n-channel organic semiconductor film is capable ofproviding on/off ratios of a source/drain current of at least 10³ ortypically of at least 10⁵. The on/off ratio is measured as themaximum/minimum of the drain current as the gate voltage is swept fromzero to 100 volts and the drain-source voltage is held at a constantvalue of 100 volts, and employing a gate dielectric.

Moreover, these properties are attainable after repeated exposure of then-type organic semiconducting layer to air before layer deposition aswell as exposure of the thin film transistor device or the channel layerto air after layer deposition.

Without wishing to be bound by theory, there are several factors thatare believed to contribute to the desirable properties of the organicsemiconductor layer containing arylene diimides compounds. Thesolid-state structure of the arylene diimide compounds described hereinexhibit good order in the layer. The molecules are packed such that theorbitals of the conjugated arylene core system containing the arylenering system or the imide carboxyl groups are able to interact withadjacent molecules, resulting in high mobility. The direction of thisinteraction has a component parallel to the direction of desired currentflow in a device using this material in the semiconductor layer. Themorphology of the layer formed by arylene diimides is substantiallycontinuous such that current flows through the material withoutunacceptable interruption. However, it is particularly advantageous thatthe arylene diimide layer is not only continuous but also exhibitspolycrystalline morphology with minimum inter-grain defects so thatcurrent flows through the material without unacceptable interruption.The stereochemistry of the substituent on the arylene diimides is suchthat they do not disrupt the intrinsic ability of these molecules topack in an effective crystalline arrangement.

The lowest lying unoccupied molecular orbital of the arylene diimidecompound is at an energy that allows for injection of electrons in thecompound at useful voltages from metals with reasonable work functions.Arylene diimides (such as naphthalene diimides and perylene diimides)described herein have a desirable lowest unoccupied molecular orbital(LUMO) energy level of about 3.0 eV to about 4.6 eV with reference tothe vacuum energy level. As known in the art, LUMO energy level andreduction potential approximately describe the same characteristics of amaterial. LUMO energy level values are measured with reference to thevacuum energy level, and reduction potential values are measured insolution versus a standard electrode. An advantage for thin filmtransistor devices is that the LUMO in the crystalline solid, which isthe conduction band of the organic semiconductor, and the electronaffinity of the solid both are measured with reference to the vacuumlevel. The latter parameters are usually different from the formerparameters, which are obtained from solution.

As indicated above, the organic solvent-soluble compositions used inthis invention comprise one or more aromatic, non-polymeric amic acidsalts that can be converted with thermal energy at relatively lowtemperatures to provide organic semiconductor compositions having one ormore of the corresponding arylene diimides compounds. In manyembodiments, the organic semiconductor layer provided by the inventionconsists essentially of the one or more arylene diimide compounds,meaning that no other components are present that are essential tosemiconductivity, and such compounds are derived from compositions thatconsist essentially of the noted aromatic, non-polymeric amic acidsalts. Still other embodiments have thin film semiconductor layers thatconsist only of the one or more arylene diimide compounds, whichcompounds are derived from the thermal conversion of the compositionthat consists of the corresponding aromatic, non-polymeric amic acidsalts.

The aromatic, non-polymeric amic acid salts used in this invention offerseveral advantages. For example, since the aromatic, non-polymeric amicacid salts are soluble in a number of organic solvents, and they can bedeposited on the surface of a given substrate from a suitable organicsolvent solution without any additional surface preparation (forexample, surface energy matching). In cases where the substrate ispolymeric, the solutions can be prepared using organic solvents ormixtures of solvents that do not have unfavorable or undesirableinteraction (for example, swelling) with the substrate. As noted above,the aromatic, non-polymeric amic acid salts can be quickly and easilyconverted to the arylene diimides at relatively low temperatures due tothe presence of the catalytic cation portion of the salt.

Thus, the aromatic, non-polymeric amic acid salts have a suitable amicacid anion and one or more suitable cations. Useful cations can beorganic or inorganic although the organic cations are generally bestbecause they are more readily decomposed during thermal conversion ofthe aromatic, non-polymeric amic acid salts to the arylene diimidecompounds. Useful inorganic cations include but are not limited to,alkali metal ions can be used as inorganic cations.

A number of organic cations can be used as counter ions to amic acidsalt anions. Useful organic cations include but are not limited to,sulfonium, ammonium, phosphonium, arsenonium, morpholinium, pyridinium,quinolinium ions, and other organic cations that would be apparent toone skilled in the art. Quaternary ammonium ions having one to fourhydrogen atoms are particularly useful and one to three valences of thecation can be filled with the same or different organic substituentssuch as alkyl, cycloalkyl, aryl, heteroaryl, fluoroalkyl, orheterocyclyl groups. In most embodiments, the ammonium cations have atleast 2 hydrogen atoms and up to two alkyl or cycloalkyl groups. Instill other embodiments, the ammonium cations have three or fourhydrogen atoms and optionally one alkyl group (such as a methyl or ethylgroup) or aryl group (such as a phenyl group).

In many embodiments, the aromatic, non-polymeric amic acid salts used inthe practice of this invention are represented by either Structure (I)or (II):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the four A₁ groups in the cations represent the same ordifferent hydrogen atom or aryl, heteroaryl, non-aromatic alkyl,alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclyl groups, and at leastone of the A₁ cation groups can be a hydrogen atom.

More specifically, Ar is a substituted or unsubstituted anthracene,naphthalene, or perylene nucleus and the four carbonyl groups areattached directly to peri carbon atoms.

The non-cation A₁, A₂, and A₃ groups can be a substituted orunsubstituted aryl group having 6 or 14 carbon atoms in the aromaticring (such as substituted or unsubstituted phenyl or naphthyl groups), aheteroaryl group having 5 to 10 carbon and heteroatoms (such asnitrogen, oxygen, and sulfur) in the aromatic ring (such as substitutedor unsubstituted thienyl, furanyl, pyridyl, pyrrolyl, and pyrazolylgroups), a branched or linear, substituted or unsubstituted alkyl grouphaving 1 to 18 carbon atoms and including substituted or unsubstitutedfluoroalkyl groups (such as CF₃ or C₃F₇) and alkylaryl groups (suchbenzyl groups), a substituted or unsubstituted cycloalkyl group at least4 carbon atoms in the carbocyclic ring, or a substituted orunsubstituted heterocyclyl group having 5 to 10 carbon and heteroatoms(such as nitrogen, oxygen, and sulfur) in the heterocyclic ring.

The cation A₁ groups can be hydrogen or independently any of the groupsdefined above for the non-cation A₁, A₂, and A₃.

Various substituents on these Ar, A₁, A₂, and A₃ groups would be readilyapparent to one skilled in the art but can include for example, alkylgroups having 1 to 6 carbon atoms (such as methyl, ethyl, pentyl, andhexyl groups), cyano, fluoro, and fluoroalkyl groups (such as CF₃).

In many embodiments, Ar is naphthalene or perylene, the non-cation A₁,A₂, and A₃ groups are independently alkyl, fluoroalkyl, alkylphenyl,phenyl, or cycloalkyl groups, which can be substituted or unsubstituted,and the four A₁ groups in the cations represent the same or differenthydrogen or alkyl, fluoroalkyl, alkylphenyl, phenyl, or cycloalkylgroups, which can also be substituted, provided that at least three ofthe A₁ cation groups are hydrogen atoms.

For example, Ar can be a substituted or unsubstituted naphthalene orperylene, and A₁, A₂, and A₃ can be independently a substituted orunsubstituted alkyl, substituted or unsubstituted fluoroalkyl,substituted or unsubstituted alkylaryl, substituted or unsubstitutedphenyl, or substituted or unsubstituted cycloalkyl group. More likely,Ar is perylene, and A₁, A₂, and A₃ are independently a substituted orunsubstituted alkyl group of 1 to 12 carbon atoms, phenyl, substitutedor unsubstituted (C₁-C₃)alkylphenyl, substituted or unsubstitutedcyclopentyl, or substituted or unsubstituted cyclohexyl group.

In still other embodiments, Ar is naphthalene or perylene and the fourA₁ cation groups are hydrogen atoms.

For all of the Structures (I), (II), (Ia), (Ib), (IIa), and (IIb)described herein, some of the desired alkylaryl groups are described inU.S. Pat. No. 7,579,619 B2 (Shukla et al.) and U.S. Pat. No. 7,198,977B2 (Shukla et al.) that are incorporated herein by reference. Somedesirable fluorinated aryl groups are described in U.S. Pat. No.7,326,956 B2 (Shukla et al.) that is also incorporated herein byreference.

Some desirable cycloalkyl groups are described in U.S. Pat. No.7,422,777 B2 (Shukla et al.) and U.S. Pat. No. 7,649,199 B2 (Shukla etal.) that are incorporated herein by reference. Some desirable arylgroups are described in U.S. Pat. No. 7,629,605 B2 (Shukla et al.) thatis incorporated herein by reference.

More specifically, some of the aromatic, non-polymeric amic acid saltsare represented by the following Structure (Ia) or (IIa):

wherein: Ar and the non-cation A₁, A₂, and A₃ groups are as definedabove, and the three A₁ groups in the cations represent the same ordifferent hydrogen atom or aryl, heteroaryl, non-aromatic alkyl,alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclyl groups, as definedabove, provided at least one of the A₁ cation groups is a hydrogen atom.

Still again, the aromatic, non-polymeric amic acid salts can berepresented by the following Structure (Ib) or (IIb):

wherein: Ar and the non-cation A₁, A₂, and A₃ groups are as definedabove, and the A₁ group in the cations represent a hydrogen atom or anaryl, heteroaryl, non-aromatic alkyl, alkylaryl, fluoroalkyl,cycloalkyl, or heterocyclyl groups.

In some embodiments of the Structure IIa and IIb compounds, Ar isnaphthalene or perylene, the non-cation A₁, A₂, and A₃ groups are thesame or different alkyl, fluoroalkyl, alkylphenyl, phenyl, or cycloalkylgroups, the cation A₁ group is a hydrogen atom or an alkyl group having1 to 18 carbon atoms (including a methyl or ethyl group).

Examples of aromatic, non-polymeric amic acid salts useful in thepractice of this invention are those listed below as Compounds I-1through I-58, all of which can be thermally converted to thecorresponding arylene diimides:

The aromatic, non-polymeric amic acid salts can be easily preparedaccording to this invention in a simple reaction scheme, and thesyntheses of several compounds are described below in the InventionExamples.

Aromatic, non-polymeric amic acid salts of general Structure Ib can beprepared by a simple, one-step reaction scheme shown in the followingEquation 1:

For example, bis-naphthalamic acid can be prepared by reacting anappropriate amine (such as a primary amine) with naphthalene dianhydrideor the corresponding naphthalene tetracarboxylic acid with astoichiometric excess (at least 4 equivalents) of an appropriate amineat ambient temperature in a suitable solvent or mixture of solvents. Theamine is provided in a stoichiometric “excess” beyond that needed tocompletely use up the amine to form an amic acid salt. The excess aminein the reaction will create an aromatic, non-polymeric amic acid salt.Similar reactions can be easily carried out using other bisanhydridesand carboxylic acids.

In another method, the aromatic, non-polymeric amic acid salt ofStructure Ia can be prepared by preparing the corresponding bis amicacid followed by reaction with 2 equivalents of an appropriate amine tomake the aromatic, non-polymeric amic acid salt according to thefollowing Equation 2:

A number of organic solvents can be used for the reactions of thetetracarboxylic acid or dianhydride with the excess amine, and thechoice of solvent is not particularly limited so long as it dissolvesthe aromatic, non-polymeric amic acid salt product. Solubility of thearomatic, non-polymeric amic acid salt depends on the nature ofassociated cation and can be controlled by modifying the counter cation.Specific examples of useful solvents for preparing amic acid saltsinclude, but not limited to, methanol, ethanol, n-propanol, n-butanol,N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone,N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine,dimethyl sulfone, hexamethyl sulfoxide, γ-butyrolactone,tetrahydrofuran, chloroform, methylene chloride, dichloroethane,acetone, ethyl methyl ketone, cyclopentanone, cyclohexanone, andanisole. These solvents can be used alone or in combination. In someinstances, even an organic solvent in which the aromatic, non-polymericamic acid salt is precipitated can be used.

In the preparation of the aromatic, non-polymeric amic acid salts, boththe cis and trans isomers of the amic acid salts can be formed (see thefollowing Equation 3).

The relative amounts of cis and trans isomers depends on a number offactors such as reaction solvent, temperature, concentration of amine,and the presence or absence of additional catalyst.

To facilitate the reaction of the tetracarboxylic acid or dianhydridewith the amine in the organic solvent, the amine can be dispersed ordissolved in the organic solvent, under stirring, and thetetracarboxylic acid or dianhydride is then added, as it is or afterdispersing or dissolving it in the organic solvent. Alternatively, theamine can be added to a solution of the tetracarboxylic dianhydride thatis dispersed or dissolved in the organic solvent. In still anothermethod, the tetracarboxylic dianhydride and the amine can be addedsimultaneously to the organic solvent. In addition, the two reactantscan be added alternatively to the organic solvent until all of thedesired amounts are in the solution or dispersion. Stirring or othersuitable agitation can be desirable to obtain a solution or dispersionof the reactants. A skilled worker would understand that still otherprocedures can be used to obtain the desired reaction product (aromatic,non-polymeric amic acid salt).

For the preparation of the aromatic, non-polymeric amic acid salts ofStructure Ib, the molar ratio of the amine reactant (that is, the totalmoles of the amine to the tetracarboxylic acid or dianhydride) isgenerally at least 4:1, or at least 5:1, or more likely at least 6:1.For the preparation of the aromatic, non-polymeric amic acid salts ofStructure IIb, the molar ratio of the amine reactant (that is, the totalmoles of the amine to the tetracarboxylic acid or dianhydride) isgenerally at least 2:1, or at least 2.2:1, or more likely at least2.5:1.

For the preparation of the aromatic, non-polymeric amic acid salts ofStructure Ia (as depicted in Equation 2), the molar ratio of the aminereactant (that is, the total moles of the amine to the tetracarboxylicacid or dianhydride) in Step 1 is generally at least 2:1, or at least2.2:1, or more likely at least 2.5:1. In the Step 2 for the preparationof the aromatic, non-polymeric amic acid salts of Structure Ia, themolar ration of the amine reactant (that is, the total moles of theamine to the amic acid) is generally 2:1, or at least 3:1, or morelikely at least 4:1.

Depending on the nature of the amine and dianhydride or carboxylic acid,the described synthesis of the aromatic, non-polymeric amic acid saltcan be carried out at very low temperatures (from −20° C. to 0° C.), atroom temperature, or at a higher temperature of from 25° C. to 100° C.The reaction of bisanhydride with the amine according to Equation 1proceeds to give the aromatic, non-polymeric amic acid salt in highyield. For this reason, the reaction can easily be scaled up to anydesired concentration. Accordingly, the concentration of the resultingproduct is generally from 1 to 50 wt. % or from 5 to 30 weight % or evenfrom 1 to 10 weight % in the reaction solution or dispersion. Thereaction can be carried out at a high concentration in the initialstage, and thereafter, more organic solvent, water, or both, can beadded to the reaction solution or dispersion to adjust theconcentration.

The aromatic, non-polymeric amic acid salt is easily converted to thecorresponding arylene diimide compound by thermal dehydration imidationring closure reaction. The temperature of the dehydration imidation ringclosure is dependent on the structure of the aromatic, non-polymericamic acid salt. However, the thermal imidation of the aromatic,non-polymeric amic acid salt in a thin film transistor device or otherarticle is generally carried out in the solid state at a temperature offrom 100° C. and up to about 400° C., or from about 120° C. to about250° C.

It can be advantageous to carry out the dehydration imidation ringclosure reaction of aromatic, non-polymeric amic acid salt in thepresence of an added catalyst in the reaction solution or dispersions.Such catalysts include be are not limited to basic catalysts such asamines such as a tertiary amine or aromatic amine. Such tertiary aminesand aromatic amines include but are not limited to, pyridine,triethylamine, tributylamine, trimethylamine, tripropylamine,diazabicyclo[1.1.1]octane, diazabicycloundecane, and trioctylamine.Mixtures of these compounds can also be used. Catalytic imidation thatproceeds at a relatively low temperature is particularly desirable. Sucha tertiary amine or aromatic amine can be present in an amount of atleast 0.5 weight % and up to and including 10 weight %, or more likelyfrom about 0.5 to about 2 weight %, based on the amic acid salt that isto be thermally converted. Thus, the composition used in this inventioncan consist essentially of an aromatic, non-polymeric amic acid salt andan amine such as a tertiary amine.

A reaction in which the imidation proceeds at a relatively lowtemperature is particularly desirable.

For example, in some embodiments of this invention, a thin film of anarylene diimide compound can be prepared with a method comprising thesteps of:

A) adding a dianhydride (as described above) to an organic solvent(described above) and stirring the resulting mixture to obtain asolution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an arylene diimide precursor that is anaromatic, non-polymeric amic acid salt,

C) adding a tertiary amine to the aromatic, non-polymeric amic acid saltsolution obtained in Step B,

D) applying salt solution of Step C to a suitable substrate (asdescribed below and particularly a metal, silicon, plastic film, glasssheet, or coated glass) to form a coating,

E) removing the organic solvent from the coating to form a thin film ofthe aromatic, non-polymeric amic acid salt, and

F) thermally converting (as described above) the aromatic, non-polymericamid acid salt in the thin film to an arylene diimide compound to forman organic semiconductor layer that is generally a thin film of fromabout 100 to about 1000 Angstroms in dry thickness.

The solvent, or mixture of solvents, can be removed in step E using anysuitable technique and equipment. Generally, the solvents are removedfrom the coating by a suitable evaporation technique at desired time andtemperature. Higher temperatures can be used in shorted times, but itdepends upon the vapor pressure of the organic solvents.

A method for preparing a thin film of an amic acid salt also comprisesthe steps of:

A) adding a dianhydride to an organic solvent and stirring the resultingmixture to obtain a solution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an arylene diimide precursor that is anaromatic, non-polymeric amic acid salt,

C) applying the amic acid salt solution to a substrate (as describedbelow) to form a coating (or thin film), and

D) removing the organic solvent from the coating to form a layer (orthin film) of the aromatic, non-polymeric amic acid salt, for example byevaporation or other technique as described above.

The resulting thin film of the aromatic, non-polymeric amic acid salt(or mixture of aromatic, non-polymeric amic acid salts) can then befurther processed or used in a suitable manner before it is thermalconverted to the corresponding arylene diimide compound.

More particularly, a method comprises, not necessarily in order, thefollowing steps:

A) providing an electrically conductive substrate (as described below),

B) providing a gate electrode material over the substrate,

C) providing a gate dielectric over the gate electrode material,

D) depositing a organic solvent solution or dispersion of an aromatic,non-polymeric amic acid salt over the gate dielectric, and

E) evaporating the organic solvent to produce a thin film of thearomatic, non-polymeric amic acid salt.

Thin films of the aromatic, non-polymeric amic acid salt can be cast orcoated from solution in which they are prepared and they can beconverted to the arylene diimide compound as a thin film by simplyheating the substrate on which it is coated.

The aromatic, non-polymeric amic acid salt can be applied or depositedonto a suitable support using any suitable technique and equipment. Forexample, it can be applied out of the solution using solution coatingtechniques (such as spin or hopper coating), solution-phase deposition,ink jet techniques, lithographic or flexographic deposition in desiredpatterns, or spray coating.

For example, the aromatic, non-polymeric amic acid salt can be thermallyconverted to the arylene diimide compound to exhibit a field effectelectron mobility that is greater than 0.0001 cm²/V.sec.

In addition, the aromatic, non-polymeric amic acid salt can be depositedto provide an amount of at least 99 weight % and up to 100 weight %based on total dry layer weight. For example, it can be deposited on thesubstrate by solution-phase deposition wherein the substrate has atemperature of no more than 250° C. during deposition. The depositionsolution can include one or more organic solvents.

Alternatively, the aromatic, non-polymeric amic acid salt can bedeposited in an organic solvent solution comprising from about 0.5 toabout 10 weight % of the aromatic, non-polymeric amic acid salt.

Thermal Conversion of Precursor to Semiconductive Compound

The thermal conversion can be carried out using various procedures andapparatus to supply the desired thermal energy (or heat) to theprecursor that is on a substrate. For example, the desired thermalenergy can be provided by one or more lasers such as those emittinginfrared radiation, microheaters, microwave heaters, and other heatingdevices that would be readily apparent to one skilled in the art. Thethermal energy can be applied in a uniform manner over the entireapplied coating of aromatic, non-polymeric amic acid salt, or thethermal energy can be applied patternwise to convert only a pattern ofthe precursor, and the non-converted precursor can then be removed in asuitable fashion (for example, by washing with a solvent in which it issoluble). As noted above, an advantage of this invention is that thearomatic, non-polymeric amic acid salts can be thermally converted atrelatively lower temperatures compared to the thermal conversiontemperatures of corresponding amic acids or amic esters.

Electronic Devices

The organic semiconductor composition described herein, when used in theform of an n-channel layer, can exhibit high performance under inertconditions as well as in air without the need for special chemicalunderlayers.

The electronic devices comprise the thin film or organic semiconductorlayer described above that is derived from the aromatic, non-polymericamic acid salts. The electronic devices can include, but are not limitedto, an organic field effect transistor (OFET), organic light emittingdiode (OLED), photodetector, sensor, logic circuit, memory element,capacitor, and photovoltaic (PV) cell. For example, the activesemiconductor channel between the drain and source in an OFET cancomprise the organic semiconducting layer. As another example, anelectron injection or transport layer in an OLED device-can comprise theorganic semiconducting layer. The aromatic, non-polymeric amic acidsalts described herein and organic semiconductor layers formed therefrom have particular utility in OFET's.

Thus, the aromatic, non-polymeric amic acid salts used in the practiceof this invention can be used in a process for the production ofsemiconductor components and electronic devices incorporating suchcomponents. In one embodiment, a substrate is provided and a layer ofthe amic acid salt composition can be applied to the substrate andelectrical contacts made with the layer. The exact process sequence isdetermined by the structure of the desired semiconductive article. Thus,in the production of an organic field effect transistor, for example, agate electrode can be first deposited on a flexible substrate, forexample an organic polymer film, the gate electrode can then beinsulated with a dielectric and then source and drain electrodes and alayer of the aromatic, non-polymeric amic acid salt can be applied ontop and then thermally converted to an n-channel semiconductor layercontaining the corresponding arylene diimide compound. The structure ofsuch a thin film transistor and hence the sequence of its production canbe varied in the customary manner known to a person skilled in the art.Thus, alternatively, a gate electrode can be deposited first, followedby a gate dielectric, then the amic acid salt layer can be applied, andfinally the contacts for the source electrode and drain electrodedeposited on the precursor layer, which is then thermally converted toan organic semiconductor layer containing the corresponding arylenediimide compound. A third structure could have the source and drainelectrodes deposited first, then the amic acid salt layer, withdielectric and gate electrode, is deposited on top. This layer can thenbe thermally converted in a suitable manner to provide the organicsemiconductor arylene diimide compound.

The skilled artisan will recognize other structures can be prepared orintermediate surface modifying layers can be interposed between theabove-described components of a thin film transistor device. In mostembodiments, a field effect thin film transistor device comprises aninsulating layer, a gate electrode, an organic semiconductor layercomprising an organic semiconducting arylene diimide compound (thermallyconverted from the aromatic, non-polymeric amic acid salt) as describedherein, a source electrode, and a drain electrode, wherein theinsulating layer, the gate electrode, the organic semiconductor layer,the source electrode, and the drain electrode are in any sequence aslong as the gate electrode, and the organic semiconductor layer bothcontacts the insulating layer, and the source electrode and the drainelectrode both contact the organic semiconductor layer.

Substrate

A substrate (also known herein as a support) can be used for supportingthe organic semiconductor thin film during manufacturing, testing, oruse. The skilled artisan will appreciate that a substrate selected forcommercial embodiments can be different from one selected for testing orscreening various embodiments. In other embodiments, a substrate can bedetachably adhered or mechanically affixed to a substrate, such as whenthe substrate is desired for a temporary purpose. For example, aflexible polymeric substrate can be adhered to a rigid glass support,which support could be removed. In some embodiments, the substrate doesnot provide any necessary electrical function for the FET. This type ofsubstrate is considered a “non-participating substrate”.

Useful substrate materials can include organic or inorganic materials.For example, the substrate can comprise inorganic glasses, ceramicfoils, polymeric materials, filled polymeric materials, coated metallicfoils, acrylics, epoxies, polyamides, polycarbonates, polyimides,polyketones,poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene)[sometimes referred to as poly(ether ether ketone) or PEEK],polynorbornenes, polyphenyleneoxides, poly(ethylenenaphthalenedicarboxylate) (PEN), poly(ethylene terephthalate) (PET),poly(phenylene sulfide) (PPS), and fiber-reinforced plastics (FRP).

A flexible substrate is used in some embodiments to allow for rollprocessing, which can be continuous, providing economy of scale andeconomy of manufacturing over flat or rigid substrates. The flexiblesubstrate chosen is capable of be wrapped around the circumference of acylinder of less than about 50 cm diameter, typically less than 25 cmdiameter, or even less than 10 cm diameter, without distorting orbreaking, using low force such as by unaided hands. The flexiblesubstrate can be rolled upon itself.

In some embodiments of the articles, the substrate is optional. Forexample, in a top construction as in FIG. 1 b, when the gate electrodeor gate dielectric provides sufficient substrate for the intended use ofthe resultant TFT, the substrate is not required. In addition, thesubstrate can be combined with a temporary support. In such anembodiment, a substrate can be detachably adhered or mechanicallyaffixed to the substrate, such as when the substrate is desired for atemporary purpose, for example, manufacturing, transport, testing, orstorage. For example, a flexible polymeric substrate can be adhered to arigid glass support, which flexible substrate can be removed.

Gate Electrode

The gate electrode can be any useful conductive material. A variety ofgate materials known in the art, are also suitable including metals,degenerately doped semiconductors, conducting polymers, and printablematerials such as carbon ink or silver-epoxy. For example, the gateelectrode can comprise doped silicon, or a metal, such as aluminum,chromium, gold, silver, nickel, palladium, platinum, tantalum, andtitanium. Conductive polymers also can be used, for example polyaniline,poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS). Inaddition, alloys, combinations, and multilayers of these materials canbe useful.

In some embodiments, the same material can provide the gate electrodefunction and also provide a support function. For example, doped siliconcan function as the gate electrode and support the OFET.

Gate Dielectric

The gate dielectric is provided on the gate electrode to electricallyinsulate the gate electrode from the balance of the OFET device. Thegate dielectric can be provided in the OFET as a separate layer, orformed on the gate such as by oxidizing the gate material to form thegate dielectric. The dielectric layer can comprise two or more layershaving different dielectric constants.

The gate dielectric should have a suitable dielectric constant that canvary widely depending on the particular device and circumstance of use.For example, a dielectric constant from about 2 to about 100 or evenhigher is known for a gate dielectric. The gate dielectric layer shouldhave a resistivity of 10¹⁴ ohm-cm or greater in OFET applications. Thegate dielectric can comprise organic polymeric materials, inorganicmaterials, and organic-inorganic composite materials. Useful polymermaterials for the gate dielectric can comprise one or more dielectricpolymers such as acrylic and styrenic polymers selected from the groupconsisting of: acrylic, styrenic and styrenic-acrylic latexes,solution-based acrylic, styrenic and styrenic-acrylic polymers, andcombinations thereof;

heteroatom-substituted styrenic polymers selected from the groupconsisting of: partially hydrogenated poly(4-hydroxy)styrene,poly(4-hydroxy)styrene, and copolymers of poly(4-hydroxy)styrene withhydroxyethyl(meth)acrylate, alkyl(meth)acrylate, styrene, andalkyl-substituted styrene wherein the alkyl group is a C₁ to C₁₈straight or branched chain alkyl group, phenol-aldehyde (co)polymers and(co)oligomers and combinations thereof. The gate dielectric can comprisea polymeric material, such as poly(vinylidene difluoride) (PVDF),cyanocelluloses, polyimides, and others known in the art. The gateelectric can comprise a plurality of layers of different materialshaving different dielectric constants.

In certain embodiments, polymer gate dielectric can possess one or moreof the following characteristics: coatable out of solution,crosslinkable, photo-patternable, high thermal stability (for example,stable up to a temperature of about 250° C.), low processingtemperatures (for example, less than about 150° C. or less than 100°C.), and are compatible with flexible substrates. Crosslinkable orphoto-patternable polymers are particularly desirable. This is becausethey provide flexibility in manufacturing methods, would easilyintegrate with solution processed device layers, and could allow forhigh-speed roll-to-roll processing. Polymers are photo-patternable ifthey include one or more crosslinking (that is, crosslinkable) groupsthat can be induced to form a crosslinked network upon exposure toradiation (most commonly, UV radiation). The exposed (crosslinkedportion of the polymer) becomes insoluble in certain solvents and theunexposed portion of the polymer can be washed away using a developingsolvent. This is an example of a negative-acting photo-patternablepolymer. It is also possible to photo-pattern a polymer that isinitially insoluble in certain solvents and that becomes soluble inUV-exposed areas upon exposure. This is an example of a positive-actingphoto-patternable polymer.

For OFET's, the polymeric dielectric layer generally has a thickness ofless than about 5000 Angstroms (Å), typically less than about 3000 Å, orless than about 2000 Å. The polymeric dielectric layer generally has athickness of at least about 500 Å or typically at least about 1000 Å.The thickness can be determined through known methods such asellipsometry and profilometry. For embedded capacitors and printedcircuit board applications, the thickness can include those describedabove for OFET's, but can also be at least 10 μm or at least 20 μm.

The term dielectric polymers herein encompasses homopolymers, copolymersderived from polymerization of two or more monomers, post-derivatized(co)polymers including graft (co)polymers, and low molecular weighthomopolymers or copolymers. The polymers can be linear, branched,hyperbranched, or dendritic.

Useful materials for the gate dielectric can comprise, for example, aninorganic electrically insulating material. Specific examples ofmaterials useful for the gate dielectric include strontiates,tantalates, titanates, zirconates, aluminum oxides, silicon oxides,tantalum oxides, titanium oxides, silicon nitrides, barium titanate,barium strontium titanate, barium zirconate titanate, zinc selenide, andzinc sulfide. In addition, alloys, combinations, and multilayers ofthese materials can be used for the gate dielectric. In addition,polymeric materials such as polyimides and insulators that exhibit ahigh dielectric constant are also suitable dielectric materials asdescribed in U.S. Pat. No. 5,981,970 (Dimitrakopoulous et al.).

Useful dielectric polymers include acrylic, styrenic, andstyrenic-acrylic latexes comprising alkyl (meth)acrylate, styrene, andalkyl-substituted styrene wherein the alkyl group is a C₁ to C₁₈straight or branched chain alkyl group. Useful optional monomers used toderive these latex-based polymers include (meth)acrylic acid,hydroxyethyl(meth)acrylate, and glycidyl(meth)acrylate. Such latexes areselected from the group: Latexes A, defined herein as one or more latexresins comprising at least 85 weight % or at least 90 weight % ofalkyl(meth)acrylate, styrene, and alkyl-substituted styrene. Usefuladditional monomers used to derive these latex resins include(meth)acrylic acid (up to 5 weight %), hydroxyethyl(meth)acrylate (up to10 weight %), and glycidyl(meth)acrylate (up to 5 weight %). Suchlatexes generally have an average particle size of less than about 150nm or less than about 100 nm.

Particularly useful dielectric polymers with high resistivity (above10¹⁴ ohm-cm) are Acrylic Latexes B and Styrene-Acrylic Latexes C andcombinations thereof. Acrylic Latexes B are defined herein as one ormore acrylic latexes comprising at least 85 weight % or at least 90weight % of methyl methacrylate or butyl acrylate or both.Styrene-Acrylic Latexes C are defined herein as one or morestyrene-acrylic latexes comprising at least 85 weight % or at least 90weight % of methyl methacrylate, butyl acrylate, or styrene, or mixturesthereof. Useful additional monomers used to derive Acrylic Latexes B andStyrene-Acrylic Latexes C include (meth)acrylic acid (up to 5 weight %),hydroxyethyl methacrylate (up to 10 weight %), and glycidyl methacrylate(up to 5 weight %). Commercial examples of acrylic and styrenic acryliclatexes useful as dielectric polymers include Joncryl® 95 and 1915(co)polymers (Johnson Polymer). Methods for synthesizing suitable latexpolymers have been reported in WO 03/099574 (Caspar et al.).

Further useful dielectric polymers include solution-based acrylic,styrenic and styrenic-acrylic polymers. Herein the term “solution-based”refers to materials that are soluble in solvents such as water or one ormore common organic solvents including alcohols, ethers, esters,ketones, and aromatic hydrocarbons. Such solution-based acrylic,styrenic and styrenic-acrylic polymers have a Mw of less than 100,000and an acid number less than about 250.

Useful dielectric polymers also include heteroatom-substituted styrenicpolymers selected from the group consisting of: partially hydrogenatedpoly(4-hydroxy)styrene, poly(4-hydroxy)styrene (PHS), and copolymers ofPHS with hydroxyethyl(meth)acrylate, alkyl(meth)acrylate, styrene, andalkyl-substituted styrene wherein the alkyl group is a C₁ to C₁₈straight or branched chain alkyl group. When a PHS homopolymer is used,the branched structure is desired and the (co)polymers have an Mw ofless than about 30,000. Partially hydrogenated PHS refers to PHSpolymers that have been hydrogenated up to about 50 equivalent % of theunsaturation within the polymer. Commercial examples include PHS-B(branched PHS homopolymer; DuPont Electronic Technologies, Dallas,Tex.), Maruka Lyncur CMM (PHS copolymer with methyl methacrylate;Maruzen Petrochemical Co., LTD. Tokyo, Japan), Maruka Lyncur CHM (PHScopolymer with hydroxyethyl methacrylate; Maruzen), Maruka Lyncur CBA(PHS copolymer with butyl acrylate, Maruzen), Maruka Lyncur CST 15, 50,and 70 (PHS copolymers with styrene, Maruzen), and Maruka Lyncur PHM-C(partially hydrogenated PHS, Maruzen).

Other useful dielectric polymers include phenol-aldehyde(co)polymers/(co)oligomers and combinations thereof that are derivedfrom mono- and bis-phenols and mono- and bis-aldehydes selected from thegroup consisting of: phenol, alkyl- and aryl-substituted phenols;formaldehyde, and alkyl-, aryl- and heteroatom-substituted aldehydes.The phenol-aldehyde resins can be further derivatized, for example, thehydroxy group converted to an ether group. Such(co)polymers/(co)oligomers have an Mw of 20,000 or less or 10,000 orless. Other useful dielectric polymers include poly(vinyl acetate)homopolymers having an Mw of 100,000 or less.

The above polymers can be plasticized for improved flexibility,adhesion, compatibilization with an IR dye, among other characteristics.In certain instances, the plasticizer can be selected from the aboveclasses of polymers. For example, a higher Tg or higher molecular weight(Mw) phenol-aldehyde polymer can be blended with a lower Tg or lower Mwphenol-aldehyde polymer. Another example is PHS blended with aphenol-aldehyde polymer. Examples of suitable plasticizers for some ofthe above classes of polymers comprise poly(ethylene)glycol, glycerolethoxylate, di(ethylene glycol)dibenzoate, and phthalate-basedplasticizers such as dibutyl phthalate. A number of potentially suitableplasticizers for various polymers and details regarding their use can befound in the following reference: “Handbook of Plasticizers,” Ed. G.Wypych, ChemTec Publishing, Toronto, Ontario, 2004.

Source and Drain Electrodes

The source electrode and drain electrode are separated from the gateelectrode by the gate dielectric while the organic semiconductor layercan be over or under the source electrode and drain electrode. Thesource and drain electrodes can be any useful electrically conductivematerial including but not limited to, those materials described abovefor the gate electrode, for example, aluminum, barium, calcium,chromium, gold, silver, nickel, palladium, platinum, titanium,polyaniline, PEDOT:PSS, other conducting polymers, alloys thereof,combinations thereof, and multilayers thereof.

The thin film electrodes (for example, gate electrode, source electrode,and drain electrode) can be provided by any useful means such asphysical vapor deposition (for example, thermal evaporation, sputtering)or ink jet printing. The patterning of these electrodes can beaccomplished by known methods such as shadow masking, additivephotolithography, subtractive photolithography, printing, microcontactprinting, and pattern coating.

The organic semiconducting layer can be located over or under the sourceand drain electrodes, as described above in reference to the thin filmtransistor articles. Useful articles can also include an integratedcircuit comprising a plurality of OFET's made by the process describedherein. The n-channel organic semiconductor layer containing theabove-described aromatic, non-polymeric amic acid salt is capable ofbeing formed on any suitable substrate that can comprise the support andany intermediate layers such as a dielectric or insulator material,including those known in the art.

Processing

Organic semiconductor layers can be readily prepared by solution coatingof an aromatic, non-polymeric amic acid salt and after the coatingsolvent is removed, thermal dehydration imidization conversion of thiscompound in the coating to the corresponding arylene diimide compound insolid thin film form. The resulting organic semiconductor layer or thelayer(s) of the gate dielectric can be deposited by spin coating. Theentire process of making the thin film transistor devices or integratedcircuits can be carried out below a maximum support temperaturegenerally at or below 450° C. or typically at or below 250° C., or evenat or below 200° C. The temperature selection generally depends on thenature of the aromatic, non-polymeric amic acid salt, support, andprocessing parameters known in the art, once a skilled artisan has theknowledge of the present invention contained herein. These temperaturesare well below traditional integrated circuit and semiconductorprocessing temperatures that enable the use of any of a variety ofrelatively inexpensive supports, such as flexible polymeric supports.Furthermore, since the aromatic, non-polymeric amic acid salts aresoluble in a number of solvents it affords flexibility in coatingformulations and conditions. This enables production of relativelyinexpensive integrated circuits containing organic thin film transistorsusing a significantly simplified process.

In cases where the gate dielectric is a polymer, both the organicsemiconductor layer and the gate dielectric layer can be deposited fromsolution, making the coating of large areas less difficult. Furthermore,the aromatic, non-polymeric amic acid salts are soluble in a number ofsolvents, providing coating and manufacturing flexibility.

In one embodiment, an FET structure of FIG. 1 a is prepared by spincoating the aromatic, non-polymeric amic acid salt layer onto thedielectric layer with pre-patterned source and drain electrodes. Inanother embodiment, an FET structure of FIG. 1 c is prepared by spincoating the aromatic, non-polymeric amic acid salt onto the substratewith pre-patterned source and drain electrodes. Heating the layer atappropriate temperature and time converts the aromatic, non-polymericamic acid salt to obtain the corresponding semiconductive arylenediimide compound. Next, a dielectric layer in the form of a polymer isspin coated onto the organic semiconductor layer followed by thedeposition of the gate electrode by vacuum deposition or liquiddeposition of a conductive metal or metal dispersion, respectively.Thermal conversion of the aromatic, non-polymeric amic acid salt to thearylene diimide compound can be accomplished as described above.

Devices in which the n-channel organic semiconductor layers describedherein are useful include thin film transistors (TFT's), especiallyOFET's. Such layers can be used also in various types of devices havingorganic p-n junctions, such as the devices described on pages 13-15 ofU.S. Patent Application Publication 2004/0021204 (Liu).

Electronic devices in which FET's and other devices are useful include,for example, more complex circuits such as shift registers, integratedcircuits, logic circuits, smart cards, memory devices, radio-frequencyidentification tags, backplanes for active matrix displays,active-matrix displays (for example liquid crystal or OLED), solar cellscomprising a multiplicity of thin-film transistors, ring oscillators,and complementary circuits, such as inverter circuits, for example, incombination with other transistors made using available p-type organicsemiconductor materials such as pentacene. In an active matrix display,a thin film transistor device can be used as part of voltage holdcircuitry of a pixel of the display. In devices containing FET's, theFET's are operatively connected in ways that are known in the art. Insome embodiments, a multiplicity of thin-film transistors are deposed ona non-participating support that is optionally flexible.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A method for preparing a thin film transistor device comprising thesteps of:

A) depositing a gate insulator layer on a electrically conductingsubstrate, and

B) depositing a layer of an aromatic, non-polymeric amic acid salt onthe gate insulator layer.

2. The method of embodiment 1 further comprising:

C) thermally converting the aromatic, non-polymeric amic acid salt toform an arylene diimide compound to form an organic semiconductor layer,and

D) depositing one or more of sets of electrically conductive sourceelectrodes and drain electrodes on the organic semiconductor layer.

3. The method of embodiment 1 or 2 comprising depositing the aromatic,non-polymeric amic acid salt is thermally converted to the arylenediimide compound to exhibit a field effect electron mobility that isgreater than 0.0001 cm²/V.sec.

4. The method of any of embodiments 1 to 3 comprising depositing thearomatic, non-polymeric amic acid salt to provide an amount of at least99 weight % and up to 100 weight % based on total dry layer weight.

5. The method of any of embodiments 1 to 4 wherein the aromatic,non-polymeric amic acid salt is deposited on the substrate bysolution-phase deposition and wherein the substrate has a temperature ofno more than 250° C. during deposition.

6. The method of any of embodiments 1 to 5 wherein the aromatic,non-polymeric amic acid salt is deposited in an organic solvent solutioncomprising from about 0.5 to about 10 weight % of the aromatic,non-polymeric amic acid salt.

7. The method of any of embodiments 1 to 6 wherein the aromatic,non-polymeric amic acid salt layer further comprises an amine catalyst.

8. The method of any of embodiments 2 to 7 wherein the aromatic,non-polymeric amic acid salt is thermally converted to the arylenediimide compound by exposing the aromatic, non-polymeric amic acid saltto a laser.

9. The method of any of embodiments 2 to 7 wherein the aromatic,non-polymeric amic acid salt is thermally converted to the arylenediimide compound by imagewise thermal exposure.

10. The method of embodiment 9 wherein the aromatic, non-polymeric amicacid salt is thermally converted using a lithographic printing method.

11. The method of any of embodiments 2 to 10 wherein the aromatic,non-polymeric amic acid salt is thermally converted at a temperature offrom about 120° C. to about 250° C.

12. The method of any of embodiments 1 to 11 wherein the aromatic,non-polymeric amic acid salt is deposited in a solution comprising oneor more organic solvents.

13. The method of any of embodiments 2 to 12 wherein each electricallyconductive source and drain electrode are spaced apart so that they areseparated by, and electrically connected with, the organic semiconductorlayer, and

forming a gate electrode spaced apart from the organic semiconductorlayer.

14. The method of any of embodiments 2 to 13 wherein the aromatic,non-polymeric amic acid salt is deposited on the substrate bysolution-phase deposition and wherein the substrate has a temperature ofno more than 250° C. during deposition.

15. The method of any of embodiments 1 to 14 wherein the aromatic,non-polymeric amic acid salt is represented by either Structure (I) or(II):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the four A₁ groups in the cations represent the same ordifferent hydrogen atom or aryl, heteroaryl, non-aromatic alkyl,alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclyl groups, provided atleast one of the A₁ cation groups is a hydrogen atom.

16. The method of any of embodiments 1 to 15 wherein the aromatic,non-polymeric amic acid salt is represented by either Structure (Ia) or(IIa):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the three A₁ groups in the cations represent the same ordifferent hydrogen atom or aryl, heteroaryl, non-aromatic alkyl,alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclyl groups, provided atleast one of the A₁ cation groups is a hydrogen atom.

17. The method of any of embodiments 1 to 16 wherein the aromatic,non-polymeric amic acid salt is represented by either Structure (Ib) or(IIb):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the A₁ group in the cations represent a hydrogen atom or anaryl, heteroaryl, non-aromatic alkyl, alkylaryl, fluoroalkyl,cycloalkyl, or heterocyclyl groups.

18. The method of any of embodiments 1 to 17 wherein the aromatic,non-polymeric amic acid salt is one or more of Compounds I-1 throughI-58 described above.

19. A method for preparing a thin film of an arylene diimide precursorcomprising the steps of:

A) adding a dianhydride to an organic solvent and stirring the resultingmixture to obtain a solution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an aromatic, non-polymeric amic acid salt,

C) applying the dianhydride solution to a substrate to form a coating,and

D) removing the organic solvent from the coating to form a layer of thearomatic, non-polymeric amic acid salt.

20. The method of claim 19 wherein, prior to step C, a tertiary aminecatalyst is added to the solution of step B in an amount of from about0.5 to about 2 weight %.

21. The method of any of embodiments 1 to 18 comprising, not necessarilyin order, the following steps:

providing the electrically conducting substrate,

providing a gate electrode material over the substrate,

providing a gate dielectric over the gate electrode material, and

depositing the aromatic, non-polymeric amic acid salt over the gatedielectric.

22. The method of embodiment 21 wherein the steps are performed in theorder listed and the electrically conductive substrate is flexible.

23. A method comprising, not necessarily in order, the following steps:

A) providing an electrically conductive substrate,

B) providing a gate electrode material over the substrate,

C) providing a gate dielectric over the gate electrode material,

D) depositing a organic solvent solution or dispersion of an aromatic,non-polymeric amic acid salt over the gate dielectric,

E) evaporating the organic solvent to produce a thin film of thearomatic, non-polymeric amic acid salt.

24. The method of any of embodiments 1 to 18 comprising, not necessarilyin order, the following steps:

providing the electrically conducting substrate,

providing a gate electrode material over the substrate,

providing a gate dielectric over the gate electrode material,

depositing the aromatic, non-polymeric amic acid salt over the gatedielectric,

converting the aromatic, non-polymeric amic acid salt to an arylenediimide compound, and

providing an electrically conductive source electrode and a drainelectrode contiguous to the organic semiconductor layer.

25. The method of embodiment 24 wherein the steps are performed in theorder listed and the electrically conductive substrate is flexible.

26. A method for preparing a thin film of an arylene diimide compoundcomprising the steps of:

A) adding a dianhydride to an organic solvent and stirring the resultingmixture to obtain a solution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an aromatic, non-polymeric amic acid salt,

C) adding a tertiary amine catalyst to the solution obtained in Step Bin an amount of from 0.5 to 2 weight %,

D) applying the solution of Step C to a substrate to form a coating,

E) removing the organic solvent from the coating to form a layer of thearomatic, non-polymeric amic acid salt, and

F) thermally converting the aromatic, non-polymeric amic acid salt to anarylene diimide compound to form an organic semiconductor layer.

27. A method of preparing a thin film of an arylene diimide compound,comprising the steps of:

A) adding a dianhydride to an organic solvent (described above) andstirring the resulting mixture to obtain a solution or dispersion,

B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an arylene diimide precursor that is anaromatic, non-polymeric amic acid salt,

C) adding a tertiary amine to the aromatic, non-polymeric amic acid saltsolution obtained in Step B,

D) applying salt solution of Step C to a suitable substrate (asdescribed below and particularly a metal, silicon, plastic film, glasssheet, or coated glass) to form a coating,

E) removing the organic solvent from the coating to form a thin film ofthe aromatic, non-polymeric amic acid salt, and

F) thermally converting the aromatic, non-polymeric amid acid salt inthe thin film to an arylene diimide compound to form an organicsemiconductor layer that is generally a thin film of from about 100 toabout 1000 Angstroms in dry thickness.

28. The method of embodiment 26 or 27 wherein the aromatic,non-polymeric amic acid salt is thermally converted using a laser.

The present invention is demonstrated by the following examples that areintended to be exemplary and not limiting in any manner.

INVENTION EXAMPLE 1 Preparation ofdi-(cyclopentylammonium)-4,8-bis-(cyclopentylcarbamoyl)-naphthalene-1,5-dicarboxylateas a mixture of trans- and cis-isomers (Compounds I-26 and I-29)

To a stirred dispersion of 1,4,5,8-naphthalene tetracarboxylic aciddianhydride (46 mg) in tetrahydrofuran (4 ml), a solution ofcyclopentylamine (mg) in tetrahydrofuran (1 ml) was added dropwise toobtain first a clear pale yellow solution that quickly turned cloudy.Stirring was continued for an additional 5 minutes then excess diethylether was added to obtain a precipitate that was filtered, washed withdiethyl ether, and dried in air.

¹H and ¹³C NMR spectra of the product were consistent with the saltbeing a mixture of cis and trans isomers. The aromatic protons of thetrans-isomer appeared as a two doublets at 7.79 ppm (J=7.60 Hz) and 7.63ppm (J ˜7 Hz); aromatic protons of the cis isomer appeared as singletsat 7.81 ppm and 7.62 ppm. From the integrated areas of the aromaticprotons, it was determined that the product was a 1:1 mixture of cis andtrans amic acid salt. ¹H NMR (CD₃OD, 300 MHz) δ(ppm)=7.81 ppm (s, 2H,cis isomer), 7.79 (2H, J=7.60 Hz, trans isomer), 7.63 (s, 2H, J=7 Hz,trans isomer), 7.62 (s, 2H, cis isomer), 4.28 (m, 2H), 3.48 (m, 2H), 2(m, 8H), 1.63 (m, 26H). ¹³C NMR (CD₃OD) δ(ppm)=174.99, 170.98, 139.81,137.82, 136.54, 128.48, 127.11, 126.82, 126.26, 126.06, 51.97, 32.30,30.88, 23.74, 23.69.

INVENTION EXAMPLE 2 Conversion ofdi-(cyclopentylammonium)-4,8-bis(cyclopentylcarbamoyl)-naphthalene-1,5-dicarboxylateas a mixture of trans and cis isomers (Compounds I-26 and I-29) toN,N′-biscyclopentyl Naphthalene Diimide in Solid State

A solution ofdi-(cyclopentylammonium)-4,8-bis(cyclopentylcarbamoyl)-naphthalene-1,5-dicarboxylatesalt in methanol (2 weight %) was spin coated on a glass plate andsolvent evaporated at 40-50° C. The thin solid film of the salt was thenheated at 180° C. for 10 minutes and resulting product dissolved inCDCl₃ and ¹H NMR spectrum recorded and compared with an authentic sampleof N,N′-bis(cyclopentyl)naphthalene diimide. The 1H NMR spectrum of theproduct obtained by solid state thermal conversion of amic acid salt wasidentical to that of the authentic sample. This clearly demonstratedthat the amic acid salt can be easily converted to the correspondingdiimide in thin solid film. ¹H NMR (CDCl₃, 300 MHz) δ(ppm)=8.72 (s, 4H),5.55 (q, 2H, J=8.2 Hz), 2.35-1.37 (m, 16H). IR spectra before and afterheating clearly showed the formation of diimide in thin solid film (seeFIGS. 2 a and 2 b). Furthermore the X-ray diffraction pattern of theN,N′-bis(cyclopentyl)naphthalene diimide prepared by solid state thermalconversion of precursor salt was identical to the powder X-raydiffraction pattern of the authentic sample (FIG. 3), confirming thehigh purity of diimide obtained by the inventive method.

OTFT Test Device Preparation Employing an Arylene Diimide Generated froman Amic Acid Salt:

Dielectric Preparation:

A heavily doped Si wafer with thermally grown SiO₂ (200 nm) dielectriclayer was used as substrate. The SiO₂ surface was modified byspin-coating a 5 weight % solution of Cyclotene 3022-35 resin (DowChemical) in mesitylene at 3000-5000 rpm. The Cyclotene resin-coatedSi/SiO₂ wafer was placed on a hot plate and gradually heated from 50° C.to 150° C. under an inert atmosphere over a period of 15 minutes.Finally, the temperature was increased to 250° C. and was held for 30minutes. Each sample was gradually cooled to room temperature over aperiod of 30 minutes. The thickness of each coated Cyclotene resin layercoated was in the range of 15 to 20 nm.

Coating of Salt Precursor and Thermal Conversion to Diimide:

A 0.5 weight % solution ofdi-(cyclopentylammonium)-4,8-bis(cyclopentylcarbamoyl)-naphthalene-1,5-dicarboxylate(as a mixture of trans- and cis-isomers of Compounds I-26 and I-29) inethanol-CHCl₃ (1:1) containing triethylamine (2 weight %) was spincoated on Cyclotene-resin modified SiO₂ surface. Sample was heated on ahotplate initially at 50° C. to remove the solvent and then temperaturewas raised to 180° C. over a period of about 5 minutes and the wafer washeated at 180° C. for 10 minutes in air. The resulting thin film ofN,N′-bis(cyclopentyl)naphthalene diimide was used as an n-typesemiconductor. The thickness of the semiconductor layer was a variablein some experiments, but was estimated to be 17-25 nm. OTFT devicesusing top source-drain contact configuration were made by depositinggold source drain contacts of thickness 60 nm through a shadow mask. Thechannel width was held at 650 μm while the channel lengths were variedbetween 50 and 150 μm.

Device Measurement and Analysis:

Electrical characterization of the devices prepared above was performedusing a Hewlett Packard HP 4145B® semiconductor parameter analyzer. Theprobe measurement station was held in a positive argon environment forall measurements with the exception of those purposely used for testingthe stability of the devices in air. For each experiment performed,between 4 and 12 individual devices were tested on each sample prepared,and the results were averaged. For each device, the drain current(I_(d)) was measured as a function of source-drain voltage (V_(d)) forvarious values of gate voltage (V_(g)). For most devices, V_(d) wasswept from 0 V to 100 V for each of the gate voltages measured,typically 0 V, 25 V, 75 V, and 100 V. In these measurements, the gatecurrent (I_(g)) was also recorded in order to detect any leakage currentthrough the device. Furthermore, for each device the drain current wasmeasured as a function of gate voltage for various values ofsource-drain voltage. For most of the devices, Vg was swept from 0 V to100 V for each of the drain voltages measured, typically 25 V, 75 V, and100 V.

The log of the drain current as a function of gate voltage was plotted.Parameters extracted from the log I_(d) plot included the I_(on)/I_(off)ratio and the sub-threshold slope (S). The I_(on)/I_(off) ratio issimply the ratio of the maximum to minimum drain current, and S is theinverse of the slope of the I_(d) curve in the region over which thedrain current is increasing (that is, when the device is turning on).

The thin film transistor devices were evaluated in an argon atmosphereusing a Hewlett-Packard 4145B® semiconductor parameter analyzer. Foreach thin film transistor device, the field effect mobility (μ) wascalculated from the slope of the (I_(d))^(1/2) versus V_(g) plot (FIG. 4a). This plot shows the square root of I_(d) vs. V_(g) and a mobility of2×10⁻⁵ cm²/V.sec was calculated from this plot. The threshold voltageV_(T)=71 V and current modulation, as can be seen from FIG. 4 a, betweenthe on and the off state of the device was about 10³.

Device Comparison with Authentic Sample:

For comparison, a similar device was prepared using an authentic sampleof the diimide. Accordingly, a 2 weight % solution ofN,N′-bis(cyclopentyl)naphthalene diimide in chloroform was spin coatedonto Cyclotene resin-modified SiO₂ dielectric. Solvent was evaporated ona hot plate and top source-drain silver contacts of thickness 60 nmdeposited through a shadow mask. The channel width was held at 650 μmwhile the channel lengths were varied between 50 and 150 μm. The fieldeffect mobility (μ) calculated from the slope of the (I_(d))^(1/2)versus V_(g) plot (FIG. 4 b) was of 1×10⁻⁴ cm²/V.sec was calculated fromthis plot. The threshold voltage V_(T)=67 V and current modulation, ascan be seen from FIG. 4 b, between the on and the off state of thedevice was about 10⁴.

This example clearly demonstrates that the semiconductive performance ofarylene diimide obtained via thin solid film thermal conversion of anaromatic, non-polymeric amic acid salt performed comparable to anauthentic diimide.

INVENTION EXAMPLE 3 Preparation ofdi-(cyclohexylammonium)-4,8-bis(cyclohexylcarbamoyl)-naphthalene-1,5-dicarboxylateas a mixture of trans and cis isomers

To a stirred dispersion of 1,4,5,8-naphthalene tetracarboxylic aciddianhydride (46 mg, 0.17 mmol) in tetrahydrofuran (4 ml), a solution ofcyclohexylamine (68 mg, 0.68 mmol) in tetrahydrofuran (1 ml) was addeddropwise to obtain first a clear pale yellow solution that quicklyturned cloudy. Stirring was continued for an additional 5 minutes, thenexcess diethyl ether was added to obtain a precipitate that wasfiltered, washed with diethyl ether, and dried in air.

¹H and ¹³C NMR spectra of the product were consistent with the saltbeing a mixture of cis and trans isomers. The aromatic protons of thetrans-isomer appeared as a two doublets at 7.78 ppm (J=7.60 Hz) and 7.63ppm (J ˜7 Hz); aromatic protons of the cis isomer appeared as singletsat 7.81 ppm and 7.61 ppm. From the integrated areas of the aromaticprotons, it was determined that the product was a 1:1 mixture of cis andtrans amic acid salt. ¹H NMR (CD₃OD, 300 MHz) δ(ppm)=7.81 ppm (s, 2H,cis isomer), 7.78 (2H, J=7.60 Hz, trans isomer), 7.63 (s, 2H, J=7 Hz,trans isomer), 7.61 (s, 2H, cis isomer), 3.90-3.78 (m, 2H), 3.0-2.86 (m,2H), 2.09-2.16 (m, 4H), 1.98-1.60 (m, 18H), 1.5-1.1 (m, 20H). ¹³C NMR(CD₃OD) δ(ppm)=175.23, 170.46, 141.38, 140.01, 137.94, 136.63, 128.46,128.43, 127.09, 126.78, 126.23, 125.97, 51.15, 49.29, 49.25, 32.47,31.04, 25.70, 25.20, 24.81.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

10 substrate

20 gate dielectric

30 semiconductor

40 source electrode

50 drain electrode

60 gate electrode

1. A method for preparing a thin film transistor device comprising thesteps of: A) depositing a gate insulator layer on a electricallyconducting substrate, and B) depositing a layer of an aromatic,non-polymeric amic acid salt on the gate insulator layer.
 2. The methodof claim 1 further comprising: C) thermally converting the aromatic,non-polymeric amic acid salt to form an arylene diimide compound to forman organic semiconductor layer, and D) depositing one or more of sets ofelectrically conductive source electrodes and drain electrodes on theorganic semiconductor layer.
 3. The method of claim 1 comprisingdepositing the aromatic, non-polymeric amic acid salt that is thermallyconverted to the arylene diimide compound to exhibit a field effectelectron mobility that is greater than 0.0001 cm²/V.sec.
 4. The methodof claim 1 comprising depositing the aromatic, non-polymeric amic acidsalt to provide an amount of at least 99 weight % and up to 100 weight %based on total dry layer weight.
 5. The method of claim 1 wherein thearomatic, non-polymeric amic acid salt is deposited on the substrate bysolution-phase deposition and wherein the substrate has a temperature ofno more than 250° C. during deposition.
 6. The method of claim 1 whereinthe aromatic, non-polymeric amic acid salt is deposited in an organicsolvent solution comprising from about 0.5 to about 50 weight % of thearomatic, non-polymeric amic acid salt.
 7. The method of claim 1 whereinthe aromatic, non-polymeric amic acid salt layer further comprises anamine catalyst.
 8. The method of claim 2 wherein the aromatic,non-polymeric amic acid salt is thermally converted to the arylenediimide compound by exposing the aromatic, non-polymeric amic acid saltto a laser.
 9. The method of claim 2 wherein the aromatic, non-polymericamic acid salt is thermally converted to the arylene diimide compound byimagewise thermal exposure.
 10. The method of claim 9 wherein thearomatic, non-polymeric amic acid salt is thermally converted using alithographic printing method.
 11. The method of claim 2 wherein thearomatic, non-polymeric amic acid salt is thermally converted at atemperature of from about 120° C. to about 250° C.
 12. The method ofclaim 1 wherein the aromatic, non-polymeric amic acid salt is depositedin a solution comprising one or more organic solvents.
 13. The method ofclaim 2 wherein each electrically conductive source and drain electrodeare spaced apart so that they are separated by, and electricallyconnected with, the organic semiconductor layer, and forming a gateelectrode spaced apart from the organic semiconductor layer.
 14. Themethod of claim 2 wherein the aromatic, non-polymeric amic acid salt isdeposited on the substrate by solution-phase deposition and wherein thesubstrate has a temperature of no more than 250° C. during deposition.15. The method of claim 1 wherein the aromatic, non-polymeric amic acidsalt is represented by either Structure (I) or (II):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the four A₁ groups in the cations represent the same ordifferent hydrogen atom or aryl, heteroaryl, non-aromatic alkyl,alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclyl groups, provided atleast one of the A₁ cation groups is a hydrogen atom.
 16. The method ofclaim 1 wherein the aromatic, non-polymeric amic acid salt isrepresented by either Structure (Ia) or (IIa):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the three A₁ groups in the cations represent the same ordifferent hydrogen atom or aryl, heteroaryl, non-aromatic alkyl,alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclyl groups, provided atleast one of the A₁ cation groups is a hydrogen atom.
 17. The method ofclaim 1 wherein the aromatic, non-polymeric amic acid salt isrepresented by either Structure (Ib) or (IIb):

wherein: Ar is an anthracene, naphthalene, or perylene nucleus and thefour carbonyl groups are attached directly to peri carbon atoms, thenon-cation A₁, A₂, and A₃ groups are independently aryl, heteroaryl,non-aromatic alkyl, alkylaryl, fluoroalkyl, cycloalkyl, or heterocyclylgroups, and the A₁ group in the cations represent a hydrogen atom or anaryl, heteroaryl, non-aromatic alkyl, alkylaryl, fluoroalkyl,cycloalkyl, or heterocyclyl groups.
 18. The method of claim 1 whereinthe aromatic, non-polymeric amic acid salt is one or more of thefollowing Compounds I-1 through I-58:


19. A method for preparing a thin film of an arylene diimide precursorcomprising the steps of: A) adding a dianhydride to an organic solventand stirring the resulting mixture to obtain a solution or dispersion,B) adding an amine to the dianhydride solution or dispersion to providea molar ratio of the amine to the dianhydride of at least 4:1 and mixingthe reactants to obtain an aromatic, non-polymeric amic acid salt, C)applying the dianhydride solution to a substrate to form a coating, andD) removing the organic solvent from the coating to form a layer of thearomatic, non-polymeric amic acid salt.
 20. The method of claim 19wherein, prior to step C, a tertiary amine catalyst is added to thesolution of step B in an amount of from about 0.5 to about 2 weight %.21. The method of claim 1 comprising, not necessarily in order, thefollowing steps: providing the electrically conducting substrate,providing a gate electrode material over the substrate, providing a gatedielectric over the gate electrode material, and depositing thearomatic, non-polymeric amic acid salt over the gate dielectric.
 22. Themethod of claim 21 wherein the steps are performed in the order listedand the electrically conductive substrate is flexible.
 23. A methodcomprising, not necessarily in order, the following steps: A) providingan electrically conductive substrate, B) providing a gate electrodematerial over the substrate, C) providing a gate dielectric over thegate electrode material, D) depositing a organic solvent solution ordispersion of an aromatic, non-polymeric amic acid salt over the gatedielectric, and E) evaporating the organic solvent to produce a thinfilm of the aromatic, non-polymeric amic acid salt.
 24. The method ofclaim 1 comprising, not necessarily in order, the following steps:providing the electrically conducting substrate, providing a gateelectrode material over the substrate, providing a gate dielectric overthe gate electrode material, depositing the aromatic, non-polymeric amicacid salt over the gate dielectric, converting the aromatic,non-polymeric amic acid salt to an arylene diimide compound, andproviding an electrically conductive source electrode and a drainelectrode contiguous to the organic semiconductor layer.
 25. The methodof claim 24 wherein the steps are performed in the order listed and theelectrically conductive substrate is flexible.
 26. A method forpreparing a thin film of an arylene diimide compound comprising thesteps of: A) adding a dianhydride to an organic solvent and stirring theresulting mixture to obtain a solution or dispersion, B) adding an amineto the dianhydride solution or dispersion to provide a molar ratio ofthe amine to the dianhydride of at least 4:1 and mixing the reactants toobtain an aromatic, non-polymeric amic acid salt, C) adding a tertiaryamine catalyst to the solution obtained in Step C in an amount of fromabout 0.5 to about 2 weight %, D) applying the solution of Step C to asubstrate to form a coating, E) removing the organic solvent from thecoating to form a layer of the aromatic, non-polymeric amic acid salt,and F) thermally converting the aromatic, non-polymeric amic acid saltto an arylene diimide compound to form an organic semiconductor layer.27. A method of preparing a thin film of an arylene diimide compound,comprising the steps of: A) adding a dianhydride to an organic solvent(described above) and stirring the resulting mixture to obtain asolution or dispersion, B) adding an amine to the dianhydride solutionor dispersion to provide a molar ratio of the amine to the dianhydrideof at least 4:1 and mixing the reactants to obtain an arylene diimideprecursor that is an aromatic, non-polymeric amic acid salt, C) adding atertiary amine to the aromatic, non-polymeric amic acid salt solutionobtained in Step B, D) applying salt solution of Step C to a suitablesubstrate (as described below and particularly a metal, silicon, plasticfilm, glass sheet, or coated glass) to form a coating, E) removing theorganic solvent from the coating to form a thin film of the aromatic,non-polymeric amic acid salt, and F) thermally converting the aromatic,non-polymeric amid acid salt in the thin film to an arylene diimidecompound to form an organic semiconductor layer that is generally a thinfilm of from about 100 to about 1000 Angstroms in dry thickness.
 28. Themethod of claim 26 wherein the aromatic, non-polymeric amic acid salt isthermally converted using a laser.
 29. A method for fabricating athin-film semiconductor device, consisting essentially of, notnecessarily in the following order, the steps of: A) applying onto asubstrate an organic solvent solution of an aromatic, non-polymeric amicacid salt and an amine catalyst to form a coating, B) evaporating thesolvent to produce a thin film of the aromatic, non-polymeric amic acidsalt, and C) heating the thin film of the aromatic, non-polymeric amicacid salt for a period of time sufficient to convert the aromatic,non-polymeric amic acid salt to form an organic semiconductor thin filmconsisting essentially of a corresponding arylene diimide compound, D)forming a spaced apart electrically conductive source electrode anddrain electrode, wherein the electrically conductive source electrodeand the drain electrode are separated by, and electrically connectedwith, the organic semiconductor thin film, and E) forming a gateelectrode spaced apart from the organic semiconductor thin film.
 30. Amethod comprising, not necessarily in order, the following steps: A)providing a substrate, B) providing a gate electrode material over thesubstrate, C) providing a gate dielectric over the gate electrodematerial, D) depositing a organic solvent solution or dispersion of anaromatic, non-polymeric amic acid salt over the gate dielectric, E)evaporating the organic solvent to produce a thin film of the aromatic,non-polymeric amic acid salt, F) heating the thin film of the aromatic,non-polymeric amic acid salt at a temperature and for a period of timesufficient to convert the aromatic, non-polymeric amic acid salt to thecorresponding arylene diimide compound to provide an organicsemiconductor thin film, and G) providing an electrically conductivesource electrode and a drain electrode contiguous to the organicsemiconductor thin film.